Principle and Function

Principle and Function

Principle

Due to the rich mixture during the cold start phase, the exhaust emissions contain an increased level of unburned hydrocarbons. The Secondary Air Injection (AIR) system improves the secondary oxidation within the catalytic converter, thereby reducing harmful emissions. The heat released by secondary oxidation shortens the start-up time of the catalytic converter considerably, as well as significantly improves emissions quality during the cold-running phase.

Function

• During cold start (with coolant temperatures +15 °C to +35 °C / +59 °F to +95 °F), Secondary Air Injection (AIR) system blows air behind exhaust valve for approximately 65 seconds. This produces an oxygen rich exhaust gas, causes after burning and reduces the heating-up phase of the catalytic converter.

• In addition, the Secondary Air Injection (AIR) system is switched on with a delay of approximately 20 seconds during idle for 5 seconds after every subsequent engine start up to max. 80 °C / 176 °F coolant temperature and is checked via On Board Diagnostic (OBD).

• The motronic control module (J220) controls the secondary air pump motor (V101) to the secondary air pump relay (J299).